Drag Has Significant Effect on MPG

[tomlink]

I drove to the beach in NC this weekend. Basically I take just one road, US 64, all the way. Even though it is one road, the speed limit moves around a lot, from a low of 35 through a few towns, to 70 on the freeway sections. I thought I'd reset my DIC to see what kind of mileage I'd get with the cruise control on for 200 miles. I was surprised when I checked it at my destination it was 25 MPG.

Now it was 95 outside and I had the AC on the whole time. But I have driven like that before and my MPG was closer to 30MPG. I was a bit concerned that perhaps there was some sort of engine malfunction. I didn't notice any hesitation or other indication of a problem.

On the way back I kept resetting the DIC in each speed zone to see if that was a factor. Other trips were always on roads with lower top speed limits.

It seems that when I was traveling about 75MPH I was getting only 24MPG. When I was going 65 that went up to 28MPG, and at 60 it was 30.5. Probably 150 miles of the trip were at 75.

I gotta say I was surprised. The car shows no sign of struggling against drag factors at 75. I thought our cars had a better drag coefficient than I observed today.

Have other folks observed something like this? Are newer models better? Mine is a 2011. It does look like the 2016 paid more attention to drag in the body design.

[Texas RattleSnake]

I drove to Tennessee this past week which is about a 230 mile trip. This was my first actual long drive in the camaro ( ss ls3 m6) so I was anxious to see what kind of mileage I could get on the highway. I don't do much highway driving. I kept it steady between 65 and 70. After I arrived It was showing 26 mpg which i was surprised. And only used about a half tank of gas

[TooCool5]

Definitely right about the drag, on a back country road at 45-50 mph I can
easily do 34-35 mpg in my LS with Airaid intake.
On the highway it goes down a few mpg at 65-70 mph.

[motorhead]

Not surprising at all... more speed more fuel consumption.

[Airmaster]

I get roughly 25 MPG driving highway between 65 and 80 MPH in the hot Florida summer. I have gotten up to 30 MPGs driving 60, but that was before my tire/wheel upgrade and my addition of a larger spoiler as well as a splitter. Both could be having a slightly negative effect, which means they are probably doing their job in producing downforce (drag being a side effect).

I thought it might be bad myself but I think its a combo of the heat, my low tire pressures (at the time, since then I brought them up a bit), and my aggressive driving...

In the city I still manage around 20 MPGs... lower if I rag on it.

What kills our cars is the weight, and yes, drag. Camaro actually has a pretty low drag coefficient but hauling around the weight just doesn't help.

[Rock-It Man]

If you are on a level road at a constant speed, most of the energy goes to overcoming drag.

If you are stopping and going in slow traffic, most of the the energy goes into accelerating the mass of the car.

[FASTDIESEL]

Got 22.8 on a tankful on the recent Power Tour. 70 MPH with air on, two occupants and a trunk-full of stuff. One tankful was only 19.7, hitting a 20 MPH headwind between Champaign and St. Louis, plus some gridlock in Champaign.

Tuning out the AFM cost about 2 MPG (highway, no change city), but is SO worth it in terms of smoothness!

[SIN R G]

Also on the Power Tour on the first half on the way to Baton Rouge I put on 1814 miles I got 19.8. I was a little surprised at that number considering on how much of that time was sitting in traffic idling. On the way home I reset it and we put on 1087 miles and I got 22.1. A lot of this was with the cruise control set at 81 or 82. I am only guessing but if we would have done the trip back and kept it at 65 I bet we would have got around 25.

[Camaro Dude]

The 4th gen had a lower Cd than the 5th Gen, so no major breakthrough here as far as wind slicing goes, lol.

Curious what the 6th gen brings to the table.

[songsj]

The 4th gen had a lower Cd than the 5th Gen, so no major breakthrough here as far as wind slicing goes, lol.

Curious what the 6th gen brings to the table.

I believe this maybe true as when I would take my foot off the gas with my 4th gen, it would coast forever. Even on a flat surface. More than any other car I've ever owned.

[Rangore]

I noticed that I lost 2 MPG by having the windows down at 70 MPH.

[Chevy_cowboy]

No kidding.

Even something as simple as a clean waxed car vs a dirty one will affect mileage. Speed certainly does, as does wind direction and speed, pavement type, tire inflation, and dozens of other factors. The biggest single factor is the nut behind the wheel though.

[WoodBoss]

That is why back in the 1970s during the gas shortage the National Speed limit was set @ 55mph.

[mth35115]

Also, the outside air temperature will affect how well an engine burns fuel, so in cold weather you will get better gas mileage. This had more of an affect on carburated cars, than modern fuel injected cars, but you will see a difference between a 60* and a 95* day.